Numerous photoreceptor devices for electrostatographic imaging systems are known including devices incorporating selenium, selenium alloys; layered inorganic photoreceptor devices; and layered organic photoreceptor devices. Examples of layered organic devices include those containing a charge transporting layer and a charge generating layer. Thus, for example, an illustrative layered organic device can be comprised of a conductive substrate, overcoated with a charge generating layer, which is in turn overcoated with a transporting layer. In a further variation of this device, the transporting layer can be overcoated with the generating layer. U.S. Pat. No. 4,410,616 discloses another variation in which a transport layer is sandwiched between two generating layers. Additional similar layers can also be added to achieve different charging characteristics.
Many systems employing configurations of these types of layers have been proposed for forming multi-color electrostatic images. Representative patents disclosing such systems include U.S. Pat. Nos. 4,378,415; 4,335,194; 4,281,051; 4,250,239 and 4,310,610. However, most of these systems use photoreceptors incorporating a trapping layer between the two photogenerating layers and/or an ambipolar transport layer in the photoreceptor architecture. These characteristics make fabrication of the photoreceptors complicated and fairly expensive. Moreover, many prior multi-color systems require complicated means for assuring that successive images are properly registered or require development cycles between charge/exposure cycles. It would, therefore, be desirable to provide a photoreceptor with an architecture which provides for multi-color image processing without the incorporation of unnecessary or expensive layers. It would also be desirable to provide such a system which simply and efficiently provides for proper registration of electrostatic images during the charge/exposure cycles.